Explanation for G’s imprecision stumbles

AS THE WORLD TURNS A 60-minute exposure of Mount Teide in the Canary Islands shows star trails, a product of Earth’s spin. Tiny deviations in Earth’s rotation rate could account for difficulties in measuring Newton’s gravitational constant, a new study suggests.

Tiny changes in Earth’s rotation rate could explain physicists’ inability to precisely measure a key fundamental constant of nature, a study in the April EPL proposes. Physicists say the idea would be extremely compelling — if not for some confusion with dates that probably derails the findings.

A graph in the paper shows that the measured values of Newton’s gravitational constant, G, peak and trough in lockstep with a nearly six-year cycle of fluctuations in the duration of Earth’s roughly 24-hour days. The researchers don’t suggest that the value of G is actually changing but say an unknown geophysical mechanism could influence experiments. An unpublished reanalysis of the data, however, makes the researchers’ argument far less convincing. It’s the latest twist in a long, frustrating effort to pin down one of the universe’s cagiest constants.

The gravitational constant is a measure of gravity’s

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